Cars, trucks, bicycles, etc., use various types of tires. When these tires are manufactured, a bag called a bladder is usually used.
In this manufacturing method, a bag known as a bladder is first inserted into an uncured tire (raw tire). The bag is then inflated by hot water or steam and the raw tire, with an inflated bladder inserted in it, is set in a mold for heating and curing to form the desired tire molding product. In this method, when the bladder is inflated, a good lubricant property is needed between the interior of the raw tire and the bladder. After curing, when the bladder is shrunk, a good mold releasing property is needed between the bladder and the internal surface of the cured tire. Hence, tests have been conducted to coat a lubricant or a mold release agent on the surface of the bladder. To date, many types of bladder lubricant compositions for tire moldings have been proposed. For example, Canadian Patent No. 1,161,422 proposes a type of lubricant composition made of polydimethylsiloxane, an alkoxysilane compound, and a zinc-family catalyst. However, this lubricant composition has several disadvantages, such as a short operating time (pot life), a weak adherent strength on the bladder, and a poor durability. On the other hand, Canadian Patent No. 1,217,293 and Japanese Kokai Patent No. 57-111393 propose lubricant compositions containing polydimethylsiloxane and polyethylene glycol and/or polypropylene glycol, etc. However, these lubricant compositions also have disadvantages, such as poor heat resistance and poor durability for long-term application.